Recently, I realized that my 30gal and my 29gal tanks were not going to be
enough to contain my "rainbow habit" ;-) so I though about getting a 55gal
tank. After a few days of looking at tanks, I decided that a 75gal tank would
be better because they essentially take up the same amount of space yet they
are able to hold more fish. 55s and 75s are both 48 inches long and they are
also the same depth. Where they differ is in their width (front to back). I
believe that 55s are 12 inches front to back while 75s are 18 inches. This
extra 6 inches does not take up much floor space and it does give you more fish
space.
John Dowden